This invention relates to contour projectors, and more particularly to contour projectors of the type having a fixed or stationary screen onto which enlarged images of workpieces are projected for observation by an operator. Even more particularly this invention relates to an improved contour projector of the type described which includes a plurality of interchangeable magnification lenses having internalized telecentric stops, and which may be indexed selectively into registry with the optical axis of the projector in order to provide considerably higher magnifications of the projected workpiece image then was heretofore possible.
Prior art contour projectors of the type described typically utilize surface illumination which is directed in one direction along the optical axis onto the surface of the workpiece that is to be inspected, and in such manner that the image of the workpiece is projected in the opposite direction along the optical axis to the screen onto which the image is to be projected. This is the most effective way of illuminating normal flat surfaces, and to view into blind cavities or recesses formed in the surfaces that are being inspected. My U.S. Pat. No. 5,402,193, for example discloses a contour projector which discloses a light source for projecting a beam of light through a beamsplitter onto one side of a workpiece, so that the image of the illuminated side of the workpiece is projected rearwardly along the optical axis to the beamsplitter, which then projects the image through a set of magnification lenses onto a stationary screen for observation by an operator.
While the projector disclosed in my above-noted U.S. patent enables near normal surface illumination by injecting light surrounding the telecentric stop of an optical relay system, this invention incorporates a conventional beamsplitter that provides true normal illumination. In addition to not requiring an optical relay, the current invention can provide illumination and imaging at much higher apertures or lower F-number, with associated higher resolution and greater brightness, than otherwise possible. In this invention, the entrance lens is essentially only half of a relay, which still includes the desireable attributes of a fixed lens and large constant working distance.
Inspection devices emobdying different magnification lenses have been developed, as disclosed for example in my U.S. Pat. No. 5,668,665. The device disclosed therein, however, is designed for transmitting images to a video camera, which in turn transmits the images to a monitor for observation by an operator or for computerized analysis. However, although such apparatus increases magnification of the images, contour projector systems of the type disclosed herein require considerably higher magnifications and larger fields than video applications of the type disclosed in my above-noted patent. And unlike the novel system disclosed herein, the above-noted video system has telecentric stops that are external on the interchangable portions of the system, and such prior system does not offer means for adjusting the exact magnification.
It is an object of this invention, therefore, to provide an improved contour projector having an optical system including a plurality of interchangeable telecentric parfocal magnification lenses which can be indexed selectively and one-by-one into registry with the optical axis of a stationary entrance lens assembly in order to project images of different precise magnifications onto the associated projector screen.
Another object of this invention is to provide an improved contour projector of the type described which employs a plurality of different magnification lenses which can be shifted selectively and one-by-one into registry with a fixed entrance lens assembly, and which eliminate the need for employing relay lenses for transmitting an image to the associated display screen, while maintaining fixed exposed lenses and a constant large working distance.
Other objects of this invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.